LONDON (Reuters) - Britain's efforts to tackle climate change and improve energy efficiency are not to blame for soaring household energy bills, the government's climate advisers said in a report on Thursday.

The report comes as five of Britain's 'Big Six' energy firms are due to sharply increase their electricity prices this year, blaming the escalating costs of government schemes to support renewable electricity generation and to help customers use less energy.

Last year "the majority of the typical household bill resulted from wholesale, transmission and distribution costs which are unrelated to the government's low-carbon policies," Britain's Committee on Climate Change (CCC) said.

The report said just over 100 pounds ($122), or around 9 percent of a household's combined gas and electricity bill, were due to government schemes to help cut harmful greenhouse gas emissions such as subsidies for renewable power generation.

However, schemes to improve energy efficiency, and help Britain reach its climate targets, saved the typical household around 290 pounds a year, the report said.

The savings largely come though the replacement of older appliances such as fridges, freezers and boilers, with ones that run on much less energy.

Greater energy efficiency has cut household gas and electricity use by 23 percent and 17 percent respectively since 2008, the CCC said.

Low carbon policies are expected to add a further 85-120 pounds a year to a typical energy bill by 2030 but the CCC said this would be more than offset by further energy efficiency improvements, which could save households an extra 150 pounds over the same timeframe.

The British government is under pressure to bring down users' electricity bills while also subsidising low-carbon generation to help meet its carbon emission reduction targets and plug a looming supply gap.

Greenhouse gas emissions in Britain have fallen by 38 percent since 1990, and the country has a legally binding target to cut them by 80 percent from 1990 levels by 2050.